President Trump walks into the Oval Office after speaking to the annual "March for Life" event in the Rose Garden. It was his last public appearance before a government shutdown.(Photo: BRENDAN SMIALOWSKI, AFP/Getty Images)

WASHINGTON — On the first day of a 16-day government shutdown in 2013, President Barack Obama appeared in the Rose Garden to accuse Republicans of taking "the entire economy hostage over ideological demands."

On the weekend of the first shutdown of his presidency, President Trump did much the same thing — but on Twitter. "Democrats are holding our Military hostage over their desire to have unchecked illegal immigration," he wrote. "Can't let that happen!"

The party in the White House has changed and the issues are different. But Trump is learning, like Obama did, that he can't sign a bill that's not on his desk, and there's no executive order that can keep the government open without congressional approval.

Instead, two days into what may be the biggest domestic crisis of his presidency, Trump remained largely on the sidelines watching a legislative process on Capitol Hill from 16 blocks away. Instead of a weekend victory lap to celebrate the one-year anniversary of his inauguration with friends and supporters, he hasn't been seen publicly since the shutdown started Saturday morning just after midnight.

He canceled a planned weekend trip to his Mar-a-Lago resort, where a $100,000-per-couple fundraiser went on without him, and hasn't left the White House since Thursday. Trump's last public remarks — other than on Twitter — were in a speech to anti-abortion protesters Friday that made no mention of the shutdown.

Since then, the only glimpse of the president came in three photos taken by an official White House photographer and released by the press office. (One showed him at the Resolute Desk, wearing a "Make America Great Again" hat and holding a phone to his ear and looking directly at the camera.) Trump has no public events scheduled Monday.

Instead, it was Vice President Pence, half a world away on a Middle East tour, speaking to the troops and to the American people about what the shutdown means.

"Despite bipartisan support for a budget resolution, a minority in the Senate has decided to play politics with military pay. But you deserve better," Pence told members of the 332nd Air Expeditionary Wing at an undisclosed military base near Syria.

"So know this: Your president, your vice president, and the American people are not going to put up with it. We’re going to demand that they re-open the government. In fact, we're not going to re-open negotiations on illegal immigration until they re-open the government and give you, our soldiers and your families, the benefits and wages you’ve earned," he said.

Trump came to office without political experience but with a decades-long career in real estate. His governing treatise was encapsulated in his 1987 book, The Art of the Deal.

White House aides insisted Sunday he was dealing behind the scenes. "The president is engaged in finding out what are the impacts of this," White House legislative director Marc Short told NBC's Meet the Press. "He's been on the phone in trying to find a resolution to it. And he had members that were to the White House just a week ago in a bipartisan, bicameral fashion to try to get past this impasse."

In one tweet Sunday, Trump suggested that Senate Majority Leader Mitch McConnell invoke the so-called "nuclear option" — changing the rules of the Senate in order to bypass a filibuster by Minority Leader Chuck Schumer. But even McConnell's office suggested that Trump's advice wasn't helpful.

On Sunday, Trump spoke to House Majority Leader Kevin McCarthy and Senate Majority Whip John Cornyn — both Republicans. Chief of Staff John Kelly and Legislative Director Marc Short made phone calls to other lawmakers, White House press secretary Sarah Huckabee Sanders said.

Republican senators, in their own way, seemed to urge Trump to stay out of the way and let the Senate work out a deal. A bill to keep the government open though Feb. 16 has already passed in the House, but is being blocked by Senate Democrats who want it to include some provision giving legal status of undocumented immigrants who entered the United States illegally as children.

"The Senate is an institution of its own, and I think we should proceed based on what we believe is the best route forward," said Sen. Susan Collins, R-Maine, when asked about Trump's role in forging a compromise.

"Someone's got to lead, and I think the Senate is the perfect body to do that," said Sen. Lindsay Graham, R-S.C.

Graham, who has become a regular Trump golf partner even as he's tried to pull the president to the center on immigration, suggested Sunday that Trump has not been well served by White House staffers on the issue. He singled out Steven Miller, the hard-line domestic policy adviser who's been a leading voice for reducing both legal and illegal immigration.

"I've talked with the president. I think his heart is right on this issue," Graham said. "As long as Stephen Miller is in charge of negotiating immigration, we're going nowhere."